<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title>let用法</title>
		<script>
		  var i=100;
		  {
			  let j=5;
		  }
		  alert(i*j);
		</script>
	</head>
	<body>
		<!--
		 onclick ,onchange
		 ondblclick,onkeydown,onmouseover,onmouseout,onmousemove
		 onload
		-->
		<button>事件</button>
	</body>
</html>
